[ticket/10854] sql server drop default constraint when dropping column

drops default columns with T-SQL before attempting drop column to
avoids sql exception.  This is a huge annoyance in UMIL scripts running
under sql server.
Merge remote-tracking branch 'remotes/Sajaki/ticket/10854' into develop-olympus

# By Sajaki
# Via Sajaki
* remotes/Sajaki/ticket/10854:
  [ticket/10854] sql server drop default constraint when dropping column